1. Field of the Invention
The present invention relates generally to a method and composition for an oil based composition, and more particularly to a method and composition for clean up of an oil based coating composition. The present invention includes a method and composition for converting an oil based composition to a water soluble or washable form so that it can be cleaned up using aqueous wash solutions. The method of the present invention also facilitates recovery of the oil based composition from the aqueous wash solution.
2. Description of the Prior Art
When working with oil based compositions, and in particular, oil based coating compositions such as inks, paints, varnishes and the like, the clean up following application of such oil based coatings usually involves use of organic solvents for the purpose of dissolving the oil based composition and removing it from application equipment, tools and the like. This creates a waste solution comprised of the organic wash solvent and the dissolved oil based composition as well as shop towels saturated with the organic wash solvent and such composition. Such a clean up process gives rise to both air and water pollution by emitting volatile organic compounds (VOCs) into the atmosphere and by creating disposal problems for the waste solvents and dissolved oil based compositions. Many of these are considered hazardous wastes whose disposal is tightly controlled.
The above problems are partially solved by using special compositions exhibiting at least limited water solubility behavior as a function of pH. These special compositions are described in applicant's copending application Ser. No. 07/946,762 filed Sep. 17, 1992, now abandoned and applicant's copending application Ser. No. 08/041,789 entitled Method of Cleaning Waste Water and Recovery of Contaminants Therefrom filed on Apr. 1, 1993, now U.S. Pat. No 5,454,956, the entirety of both being incorporated herein by reference. By using these specially formulated compositions, the water solubility of such compositions can be selectively controlled and converted by adjusting the pH of the wash solution. This, in turn, facilitates clean up of these special compositions with aqueous wash solutions and removal and recovery of such compositions by filtration or other known separation techniques.
A problem continues to exist, however, with respect to the clean up of oil based compositions, and in particular oil based coating compositions which do not exhibit pH dependent water solubility behavior. U.S. Pat. Nos. 5,009,716 and 5,104,567 issued to Gerson and Staehr, respectively, have attempted to address this problem with respect to the clean up of oil based lithographic ink compositions. Both of these patents are directed principally to the use of wash or clean up solutions generally compatible or soluble with the ink composition, but which do not contain the undesirable VOCs. Specifically, U.S. Pat. No. 5,104,567 discloses the use of a vegetable oil/emulsifier blend to clean the equipment, while U.S. Pat. No. 5,009,716 discloses the use of fatty acids as a carrier for various nonionic surfactants. In both applications, relatively large quantities of wash solutions are required to fully clean and flush the equipment. Further, when clean up is completed, many of the same problems of biodegradability, environmental and disposal exist with respect to the wash solution and removed ink composition.
Accordingly, a need continues to exist for a clean up method and composition for oil based coating compositions, and more particularly, a clean up method for oil based coating compositions which do not exhibit pH dependent water solubility. A need also exists for recovering such oil based compositions from spent wash solutions and the like used in the clean up process, thereby further minimizing pollution and hazardous waste concerns.